Please wait while the transcript is being prepared...
Hello. I'm Richard Cornall.
I'm the Nuffield Professor of Clinical Medicine at the University of Oxford,
and I'm going to talk to you today about B-cell biology.
A good place to start is an overview of the function of B-cells,
which are called B-cells because they were discovered in
the bursa of Fabricius in poultry.
B-cells are characterised,
of course, by a B-cell receptor,
which doesn't itself signal but is associated with
Ig-alpha and -beta chains which contain immunoreceptor tyrosine-based activation motifs,
also known as ITAMs.
I'm not going to discuss the actual signaling mechanisms in detail here today.
The mode of B-cell activation is actually quite controversial,
at least in vitro activation is by
cross-linking and increasing the density of kinases relative to phosphatases.
But in vivo, most B-cells, it's now
appreciated, encounter antigen probably on the surface of other cells,
and how that operates at low density is not entirely known.
We look at the individual functions of B-cells.
The most well known is,
of course, antibody secretion,
and this arises through B-cells being activated and then differentiating into
plasma cells which secrete antibody
either on the short-term or over long-term in the bone marrow.
The second function of B-cells is to bind
antigen through the B-cell receptor and present them
on MHC class II receptors to activate the T-cell and obtain T-cell help.
Third function, which has been appreciated more recently is to transport antigen
within lymph nodes and the spleen particularly notably on complement receptors.
The fourth function of B-cells is to secrete cytokines.
In particular, some B-cells secrete IL-10,
and these cells are defined by some groups as being regulatory B-cells.
But unlike regulatory T-cells,
there's no transcription factor that has been
identified to define them as a unique subset.
These functions may be overlapping with other activatory functions of
B-cells and the plasticity of the B-cell subsets is not as yet clearly defined.